It is known that various combustible waste materials, for example, used tires, organic material wastes and oil waste, are utilized for generating heat by heat-decomposing them and by burning the resultant combustible substances. However, this burning of the combustible substances results in generation of a combustion gas containing various harmful substances, for example, oxides of sulphur, their derivatives, chlorine, chlorine compounds and carbon monoxide. Therefore, in order to prevent environmental pollution due to the harmful combustion gas, it is necessary to treat the combustion gas to eliminate or convert the harmful substances to harmless substances. This treatment needs special treating equipment and is expensive. Also, the heat-decomposing of the combustible waste materials and the burning of the combustible gas produce various incombustible residues. Therefore, it is necessary to treat the residues in such a manner that no environmental pollution is caused by the treatment.
Under the above-mentioned circumstances, it is strongly desired to provide a method and apparatus effective for treating the combustible waste materials without environmental pollution.
It was discovered by the inventors of the present invention that not only the combustible waste materials can be utilized as a heat source for producing a cement clinker, but also, the incombustible solid residues and harmful gases generated from the combustible waste materials have no harmful effects on the resultant cement clinker.